Anti-theft device using code type transponder

ABSTRACT

A method for registering a new key in an anti-theft device allows the registration of a new key having a code type transponder from which authentication data once written cannot be read out or written over. An ECU communicates with a transponder of a registered key such as a master key and allows an engine to be started when the result of a collating function data stored in an EEPROM of the ECU with function data written in the transponder is a match. When function data is to be written into a transponder of an unregistered new key, the ECU first communicates with the transponder of the registered key and, when the result of collation of the function data stored in the EEPROM and the function data written in the transponder of the registered key is a match, writes function data stored in the EEPROM into the transponder of the new key.

CROSS-REFERENCE TO RELATED APPLICATION

This application is related to Japanese Patent Application No. Hei8-271099, incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a method and a device with which it ispossible to carry out registration of a new key, i.e. a key which is notalready a registered key such as a master key, in an anti-theft device.

2. Description of Related Art

To enable a vehicle to be used by a number of different people, keysmade by copying a master key are sometimes newly added to existing keysfor starting the engine of or locking and unlocking doors of thevehicle. In the case of a vehicle having an anti-theft function, whennewly adding a key it is necessary to register the new key with anelectronic control unit (hereinafter abbreviated to ECU) having ananti-theft function by conducting communication between the ECU and atransponder disposed inside the new key.

In conventional new key registration, authentication data pre-writteninto a R/O (read-only) transponder disposed inside the new key is readout from the transponder and this data is transmitted to the ECU andwritten and stored in the ECU.

However, recently, to prevent the copying of keys by thieves, code typetransponders, with which once authentication data has been written inthe transponder the authentication data cannot be written over or readout, save started to be used.

With a code type transponder, since the authentication data cannot beread out, there is the problem that when the conventional method is usedit is not possible to register a new key having a code type transponderin the ECU.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a methodand a device with which it is possible to register a new key having acode type transponder.

The above object is achieved according to an aspect of the presentinvention by providing a method for registering a new key in ananti-theft device including preparing a new key having a transponder inwhich authentication data has not been written, conducting communicationbetween a transponder of a registered key and an electronic control unithaving an anti-theft function, and determining if the communication wasconducted correctly, enabling registration of a new key when it isdetermined that the communication was conducted correctly, and, whenregistration of a new key is enabled, conducting communication betweenthe transponder of the new key and the electronic control unit andwriting registered key authentication data stored in the electroniccontrol unit into the transponder of the new key. In this way, by usingthe authentication data of the master key stored in the ECU, even a newkey having a code-type transponder can be appropriately registered.

By making the collation of a pre-registered master key a condition ofregistration of a new key it is possible to set a restriction on theregistration of new keys. That is, for example, when the anti-theftdevice is applied to a vehicle, in the case of a rental car or and thelike a registered key is loaned out together with the vehicle for therental period, but if this registered key is not a master key then newkeys being registered unlawfully using this loaned-out registered keycan be prevented.

Whether each of a number of electronic keys having the sameauthentication data is a master key or a sub-key can be distinguished bymeans of a key identification code assigned uniquely to each key.

Other objects and features of the present invention will appear in thecourse of the description thereof, which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional objects and advantages of the present invention will be morereadily apparent from the following detailed description of preferredembodiments thereof when taken together with the accompanying drawingsin which:

FIG. 1 shows the construction of an anti-theft device according to afirst preferred embodiment of the invention;

FIGS. 2A and 2B are flowcharts showing specific processing of a CPU inFIG. 1;

FIG. 3 is a flowchart showing details of registration mode processing inFIG. 2A;

FIG. 4 shows a relationship of correspondence between a master key, newkeys and content stored in an EEPROM in FIG. 1;

FIG. 5 is a view showing the construction of a second preferredembodiment of the invention;

FIG. 6 is a flowchart showing specific processing carried out by CPUs inFIG. 5;

FIG. 7 is a flowchart showing function data, etc. writing in FIG. 6;

FIG. 8 is a flowchart showing function data, etc. reading in FIG. 6; and

FIG. 9 is a flowchart showing processing carried out by a checker inFIG. 5.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EXEMPLARY EMBODIMENTSFirst Embodiment

The construction of an anti-theft device for a vehicle is shown in FIG.1.

A key (a master key or another registered key; in the followingdescription, a master key) 10 has a built-in transponder 10a. Thistransponder 10a is a code type transponder in which is written functiondata serving as authentication data and which, when receiving anexcitation signal (for example, a sine wave of a predeterminedfrequency) from the vehicle side, stores energy of the excitation signalin a capacitor and operates with this energy as a power supply.

On the vehicle side there are provided an ECU 20 having an anti-theftfunction and an amplifier circuit 21 for receiving an excitationstarting signal from the ECU 20 and transmitting an excitation signal tothe master key 10. The ECU 20 is made up of a CPU 20a, a ROM 20b, a RAM20c, an input/output buffer 20d, an input/output circuit 20e and anEEPROM 20f. The same function data as the function data stored in thetransponder 10a is stored in this EEPROM 20f.

The ECU 20 communicates with the transponder 10a of the master key 10and collates the function data stored in the EEPROM 20f with thefunction data written in the transponder 10a and, when it determinesthat result of this collation is a match, enables the engine to bestarted. That is, it commences control of the injector 23 and theignitor 24 by way of the driving circuits 20g, 20h.

In the following description, the function data written in thetransponder 10a will be written Ft(X) and the function data stored inthe EEPROM 20f will be written Fe(X).

The communication and the collation of function data between the ECU 20and the transponder 10a are carried out in the following way.

First, the CPU 20a outputs an excitation starting signal to theamplifier circuit 21 and thereby causes an excitation signal to betransmitted from an antenna 22 to the transponder 10a of the master key10. After a predetermined time (for example, 50 ms) the CPU 20a outputsan excitation stopping signal to the amplifier circuit 21 and therebystops the transmission of the excitation signal from the antenna 22. Asa result of this transmission of the excitation signal for apredetermined time, the transponder 10a becomes operational.

After that, the CPU 20a outputs query data X (a set of data generatedusing random numbers; different data every time) to the amplifiercircuit 21. The amplifier circuit 21 converts "1" and "0" signal groupdata from the CPU 20a into frequencies (for example, frequency B for "1"and frequency C for "0"), and transmits this to the transponder 10a fromthe antenna 22.

The transponder 10a uses the function data Ft(X) to calculate responsedata Yt from the query data X and the function data Ft(X), and transmitsthis to the antenna 22 as a data group of the frequencies B and C. Theamplifier circuit 21 converts the frequency data received by the antenna22 into a data group of "1" and "0" and outputs this to the CPU 20a. Asthe function data Ft(X), for example, a four-rule operator such asFt(X)=(x² +x)/5+X/2+x^(-1/2) + . . . can be used.

The CPU 20a also obtains response data Ye from the query data Xtransmitted to the transponder 10a and the function data Fe(X) (which isthe same function data as that of the transponder 10a if the transponder10a is a correct transponder) stored in the EEPROM 20f.

The CPU 20a then compares the two sets of response data Yt and Ye, andif they match makes the determination "correct transponder" (thefunction data in the transponder 10a and the function data stored in theEEPROM 20f are the same) and enables the engine to be started, and ifthey do not match prevents the engine from operating.

Next, the operation of the CPU 20a will be described with reference tothe flowchart of FIG. 2A showing specific processing carried out by theCPU 20a.

When the master key 10 is inserted into a key cylinder and a key switch(IG switch) is turned on, the electrical system shown in FIG. 1 receivespower from a vehicle battery and becomes operational.

First, normal operation for starting the engine using the master key 10will be described.

When the power supply is switched on, an excitation signal and querydata X are transmitted to the transponder 10a (Step 101) and thenresponse data Ye is obtained from the query data X and the function dataFe(X) stored in the EEPROM 20f (Step 102) and also response data Yt isread out from the transponder 10a (step 103).

Data collation comparing the two sets of response data Yt, Ye is thencarried out (step 104). When the collation result is a match and keyidentification codes which will be further discussed later also match,the transponder 10a is determined to be a "correct transponder" andprocessing goes through a registration mode determination (step 105;this processing will be discussed later) and then carries out ignitionand fuel injection control of the engine (step 106). However, when thecollation result is a mismatch the processing of steps 101 though 104 isrepeated, and when the number of failures to match reaches apredetermined number, the determination of a step 107 becomes YES andthe determination "abnormal transponder" is made and it is confirmedfrom the outputs of the driving circuits 20g, 20h that ignition and fuelinjection are being prohibited (step 108) and control processing otherthan engine control (for example, processing displaying the abnormalitywith an LED or the like) is executed (step 109). Thus, in this case, theengine is not operated.

As will be understood from the foregoing description, using the functiondata written in the transponder 10a of the master key 10 it is possibleto prevent theft of the vehicle.

Next, the case of registering a new key having its shape copied from theshape of the master key will be discussed.

In this case, the master key 10 is inserted into the key cylinder, theECU 20 is operated and confirmation of the master key 10 is carried out.First, when the power supply is switched on by the insertion of themaster key 10, the CPU 20a communicates with the transponder 10a of themaster key 10 and determines whether or not communication has beenconducted correctly (the processing of steps 101 through 104).

When it is determined that communication has been conducted correctly,after this determination, it is determined whether or not within apredetermined time (for example 10 seconds) a registration operation forcarrying out registration of a new key has been carried out (step 105).For example, it is determined whether or not a predeterminedregistration operation such as turning the IG switch on and off threetimes or turning a door switch on and off four times has been carriedout by a user (operator registering a new key). When this kind ofregistration operation is carried out, new key registration is enabledand registration mode processing 200 is executed. When the master key 10is used to operate the starter, the determination of step 105 is NO andimmediate engine starting is made possible.

The specific processing of this registration mode processing 200 isshown in FIG. 3.

After carrying out the registration operation described above, the userreplaces the master key 10 in the key cylinder with a new key. Becauseat the time of this key replacement the key switch is temporarily turnedoff, when processing enters the registration mode, first, power supplyholding processing is carried out (step 201). In this case, a powersupply holding circuit (not shown) is operated to maintain the powersupply to the ECU 20 for a predetermined time.

After that, the CPU 20a confirms that the master key 10 has beenreplaced with a new key (step 202). For example, the key replacement canbe confirmed using a key insertion switch (not shown) detecting thestate of insertion of a key into the key cylinder.

Next, an excitation signal is transmitted to the transponder of the newkey and that transponder is thereby rendered operational (step 203), andthe function data Fe(X) stored in the EEPROM 20f is transmitted to thetransponder of the new key and written into the transponder as functiondata Ft(X) (step 204). After that, query data X is prepared and responsedata Ye is obtained using the function data Fe(X) stored in the EEPROM20f (step 205), and also the query data X is transmitted to thetransponder of the new key and response data Yt based on the functiondata Ft(X) just written is read out (step 206).

Data collation comparing the two sets of response data Yt, Ye is thencarried out (step 207). If the collation result is a match, it isinferred that the function data Ft(X) has been correctly written intothe new key and then a key identification code (key number) is writteninto the transponder of the new key (step 208) and the same keyidentification code is also written into the EEPROM 20f (step 209). Whenthe key identification code is entered into the new key, so that keyshaving the same key identification code are not made, a keyidentification code which has not been used before is set. For example,with respect to a vehicle in which key identification codes 1 to 5 arepreset, at the time of addition of new keys, key identification codesother than 1 to 5, such as 6, 7, . . . , are set.

Also, lock processing for writing a lock code into the transponder ofthe new key is carried out, and further writing of data into thetransponder is thereby rendered impossible (step 210). After that, thefact that the new key has been registered is made known to the user by adisplay device such as an LED (step 211).

After that, when it is ascertained that the new key has been removed andbeen replaced with another new key within a predetermined time, thedetermination of step 212 becomes YES and the registration processing ofstep 203 onward is carried out with respect to the other new key.

When it is determined in step 207 that the data collation result is amismatch, the fact that the new key has not been registered is madeknown to the user by displaying means such as an LED (step 213).

Therefore, by looking at the LED or other displaying means, the user cancheck whether or not registration of the new key has been carried out.

In the above-mentioned steps 104 and 207, data collation carried out bycomparing the two sets of response data Yt, Ye was described; however,the key identification code written into the transponder is read out anddetermination of whether or not that key identification code matches anyof the key identification codes stored in the EEPROM 20f is also carriedout, and the collation result is deemed to be a match when both theresponse data and the key identification code match.

The correspondence relationship between the master key 10, new keys 11,12 . . . and the stored content of the EEPROM 20f is shown in FIG. 4.The new keys 11, 12 . . . respectively have built in transponders 11a,12a. . . Function data Fe(X) common to all the keys is stored in theEEPROM 20f. Therefore, the storage capacity of the EEPROM 20f can bemade much smaller than when function data Fe(X) is stored individuallywith respect to each of a plurality of keys. Also, since when theresponse data is being produced, the computation of step 102 need onlybe carried out for one set of function data, reduction of the processingload is possible. Key identification codes are also stored in the EEPROM20f in correspondence with the master key 10 and the new keys 11, 12. ..

As a result of a key identification code for each key being stored inthe EEPROM 20f in this way, when a key is lost, if the keyidentification code of that key is erased from the EEPROM 20f, even ifthe lost key were to be used, because its key identification code wouldnot match any key identification code stored in the EEPROM 20f, theft ofthe vehicle would be prevented.

In the first preferred embodiment described above, registration of a newkey is enabled when collation of any already registered key is carriedout; however, alternatively, collation of a pre-registered master keymay be made a condition of registration of a new key, so as to place arestriction on the registration of new keys. This modified version ofthe first preferred embodiment will be described below.

In the case of this modified version, after (on the basis of the datacollation of step 104 shown in FIG. 2A) the result of the collation ofthe two sets of response data Yt, Ye is a match and the keyidentification code also matches and the determination "correcttransponder" is made, a step 104a of distinguishing (on the basis of thekey identification code) whether the key in the key cylinder is a masterkey or a sub-key is provided as shown in FIG. 2B, and when the key isrecognized as a master key processing goes through the registration modedetermination processing of step 105 and shifts to the engine controlprocessing of ignition and fuel injection of step 106 as describedabove; but, when the key in the key cylinder is recognized as a sub-key,processing shifts directly to step 106. In this case, in theabove-mentioned key distinguishing step, for example the key having thekey identification code registered first in the EEPROM 20f at the timeof shipping of the vehicle is recognized as the master key and any keynewly registered thereafter is recognized from its key identificationcode as a sub-key.

By making collation of a pre-registered master key a condition ofregistration of a new key and thereby placing a restriction on theregistration of new keys as in this modified version of the firstpreferred embodiment of the invention, when in the case of a rental caror the like a registered key is also loaned out during the vehiclerental period, if this loaned-out key is made a sub-key it is possibleto prevent a new key being registered unlawfully.

In the above, an example wherein when a new key is registered usingcollation of a master key the new key is registered as a sub-key wasdescribed, but the invention is not limited to this and of course aconstruction may be adopted wherein it is determined at the time ofregistration of the new key that a predetermined operation has beencarried out on, for example, a switch of the vehicle, and the new keymay be selectively registered as a master key or a sub-key.

Also, although the preferred embodiment described above was an examplewherein the authentication data (the function data Ft(X)) of all of aplurality of keys registered with respect to a single ECU 20, i.e. withrespect to one vehicle, was the same and one corresponding function dataFe(X) was stored in the EEPROM 20f, the invention can be applied also ina case where for example there are a plurality of original master keysand each has different authentication data. In this case, the sameauthentication data as that of the master key used for the collation atthe time of registration of a new key is written into the new key andkeys having the same authentication data are recognized as a master keyor a sub-key by the ECU 20 using the unique key identification codeassigned to each key.

Second Embodiment

In the preferred embodiment described above, if the ECU 20 fails (forexample, if the driving circuits 20g, 20h fail), the ECU 20 might bereplaced with another ECU. In this case, unless the function data andkey identification code (hereinafter referred to as function data, etc.)written in the registered keys such as the master key (in this preferredembodiment, also, the case of a master key will be used for thedescription) are stored in the new ECU, it will not be possible tocontinue to use the master key in the same way as before.

However, because the master key uses a code type transponder, it is notpossible to read out the content written in it. Also, due to the lockapplied after the writing of the data, the function data, etc. cannot beoverwritten. Consequently, methods involving reading out the contentwritten in the code type transponder and methods involving resetting thefunction data, etc. in the new ECU using the master key cannot be used.

To overcome this, in this preferred embodiment, in the failed ECU 20,collation using the master key is carried out, and when the collationresult is a match the function data, etc. stored in the EEPROM 20f iswritten into the new ECU so that the master key can be used with the newECU in the same way as before.

A configuration for writing function data, etc. stored in the EEPROM 20fof a failed ECU 20 into a new ECU 30 is shown in FIG. 5.

The new ECU 30 is of the same construction as the failed ECU 20 and thushas the constituent elements 30a to 30h shown in the Figure. Also,function data, etc. stored in the EEPROM 20f of the failed ECU 20 can bewritten into the EEPROM 30f of the new ECU 30 by way of a checker 40.This checker 40 is a device originally used, for example, for readingdiagnostics codes or carrying out RAM information testing work, and isconstructed to carry out writing of function data, etc. into the new ECU30 as well as these processes.

Processing executed by the CPU 20a in the ECU 20 and the CPU 30a in theECU 30 (the CPUs 20a, 30a both execute the same processing) is shown inFIG. 6. It differs from the processing of FIGS. 2A and 2B and FIG. 3 ofthe first preferred embodiment in the point that the steps 100, 110, 300and 400 have been added.

An initial code is originally stored in the EEPROM, and when storing offunction data, etc. with a master key is carried out the function data,etc. is written over that initial code. Therefore, not the initial codebut function data is stored in the EEPROM 20f, whereas the initial codeis stored in the EEPROM 30f of the ECU 30.

Consequently, when power is supplied to the ECU 20, ECU 30 (e.g., powerfrom a vehicle battery or from an outside power source), in the CPU 30aof the new ECU 30, when step 100 is reached, the determination thereofis YES and function data, etc. write processing 300 (the detailedprocessing of which is shown in FIG. 7) is executed, and in the CPU 20aof the failed ECU 20, when step 100 is reached, the determinationthereof is NO and the same collation of function data, etc. as thatdescribed in the first preferred embodiment is carried out, and when arequest to read out function data, etc. has been issued from the checker40 function data, etc. readout processing 400 (the detailed processingof which is shown in FIG. 8) is executed.

Processing carried out by the checker 40 is shown in FIG. 9.

When power is supplied to the checker 40, it first determines whether ornot it is in ECU replacement mode (step 501). The ECU replacement modedetermination is carried out on the basis of whether or not a user hasoperated an ECU replacement switch (not shown). When it is not in ECUreplacement mode, the original operation of the checker 40 mentionedabove is carried out (step 510), but when it is in ECU replacement modeit outputs a request for readout of function data, etc. to the CPU 20a(step 502).

When it receives a readout request from the checker 40, the CPU 20aexecutes the function data, etc. readout processing 400 shown in FIG. 8and first reads out the function data, etc. stored in the EEPROM 20f andsends it to the checker 40 (step 401).

The checker 40 receives the function data etc. sent from the CPU 20a(step 503) and determines whether or not the function data, etc. fromthe CPU 20a has been correctly read out (step 504). When it has beencorrectly read out, the checker 40 outputs a function data, etc. writerequest to the CPU 30a and writes the function data, etc. into the CPU30a (step 505).

When the write request is outputted from the checker 40, the CPU 30astores that function data, etc. in the EEPROM 30f (step 302). Afterthat, to confirm whether or not the function data, etc. has beencorrectly written, the CPU 30a reads the stored function data, etc. fromthe EEPROM 30f and sends it to the checker 40 (step 303).

The checker 40 sends the function data etc. sent to it from the CPU 30ato the CPU 20a (step 506).

When the CPU 20a receives the function data, etc. sent from the CPU 30afrom the checker 40 (step 402), it collates that function data, etc.with the function data, etc. stored in the EEPROM 20f (step 403). If thecollation result is a match, the CPU 20a sends a "writing OK" report tothe checker 40 (step 404) and erases the function data, etc. stored inthe EEPROM 20f. If the collation results do not match, it sends a"writing NG" report to the checker 40 (step 406). The reason for erasingthe function data, etc. stored in the EEPROM 20f is to avoid producing aduplicate ECU.

The checker 40 identifies the information received from the CPU 20a(step 507), and when it is a "writing OK" report, sends notification tothe effect that the collation result is a "match" to the CPU 30a (step508), and when it is a "writing NG" report, sends notification to theeffect that the collation result is a "mismatch" to the CPU 30a (step509).

The CPU 30a recognizes the information showing the collation result fromthe checker 40 (step 304), and when the collation result is a "match"ends function, data etc. writing and when the collation result is a"mismatch", infers that there has been a writing failure and clears thefunction code stored in the EEPROM 30f and carries out processing toreturn to the initial code (step 305). This is because if the functioncode is not returned to the initial code, it is not possible to carryout writing again.

As will be clear from the above description, with this preferredembodiment, when the ECU 20 fails, it is possible to write the functiondata, etc. stored in the EEPROM 20f of the failed ECU 20 into a new ECU30 and therefore it is possible to use the same keys as before with thenew ECU 30.

Although the present invention has been fully described in connectionwith the preferred embodiments thereof with reference to theaccompanying drawings, it is to be noted that various changes andmodifications will become apparent to those skilled in the art. Forexample, the present invention is not limited to application to vehicleshaving engines, and for example can also be applied to vehicles such aselectric vehicles not having engines, and can be applied to mobilebodies other than vehicles--for example, boats. Such changes andmodifications are to be understood as being included within the scope ofthe present invention as defined by the appended claims.

What is claimed is:
 1. A method for registering a new key in ananti-theft device, comprising:preparing a new key having a transponderin which authentication data has not been written; conductingcommunication between a transponder of a registered key and anelectronic control unit having an anti-theft function, and determiningif the communication was conducted correctly; enabling registration of anew key when it is determined that the communication was conductedcorrectly; and when registration of a new key is enabled, conductingcommunication between the transponder of the new key and the electroniccontrol unit and writing registered key authentication data stored inthe electronic control unit into the transponder of the new key.
 2. Amethod for registering a new key in an anti-theft device according toclaim 1, further comprising:after the writing is carried out, conductingcommunication between the transponder of the new key and the electroniccontrol unit and checking whether or not the authentication data hasbeen written into the transponder of the new key correctly; andinforming an operator registering the new key of the result of thecheck.
 3. A method for registering a new key in an anti-theft deviceaccording to claim 1, wherein:conducting communication between thetransponder of the registered key and the electronic control unit isdone through transmission of communication data; enabling registrationof the new key includes disengaging an anti-theft mode whenauthentication data stored in the transponder, different from thecommunication data, is identical to authentication data stored in theelectronic control unit; and writing authentication data stored in theelectronic control unit into the transponder of the new key is performedwhen a new key is subsequently placed in communication with theelectronic control unit.
 4. A method for registering a new key in ananti-theft device according to claim 1, wherein:conducting communicationbetween the transponder of the registered key and the electronic controlunit includestransmitting query data from the electronic control unit tothe transponder of the registered key, and preparing response data basedon authentication data stored in the transponder and the transmittedquery data, and transmitting the prepared response data to theelectronic control unit from the registered key transponder; determiningif communication between the transponder of the registered key and theelectronic control unit was conducted correctly includes, at theelectronic control unit, preparing response data based on the query dataand the authentication data stored in the electronic control unit, andcomparing the response data at the electronic control unit with theresponse data sent from the transponder; and writing the authenticationdata stored in the electronic control unit into the transponder of thenew key is done when the response data at the electronic control unitand the response data sent from the transponder are identical.
 5. Ananti-theft device comprising:an electronic control unit having storingmeans for storing authentication data of a registered key, theelectronic control unit being for conducting communication with atransponder of a registered key and collating the authentication datastored in the storing means with authentication data written in thetransponder, and determining if the result of the collation is a match,and when the collation result is a match, making starting of an enginepossible; wherein when authentication data is to be written into atransponder of a new key, the electronic control unit conductscommunication with the transponder of the registered key and collatesthe authentication data stored in the storing means with theauthentication data written in the transponder of the registered key,and when the result of the collation is a match, allows the writing ofauthentication data into the transponder of the new key.
 6. Ananti-theft device according to claim 5, wherein:the electronic controlunit comprises means for writing a key identification code of the newkey into the transponder of the new key and the storing means; and theelectronic control unit collates the authentication data and the keyidentification codes and enables the engine to be started when theresult of the collation is a match.
 7. An anti-theft device according toclaim 5, wherein:the electronic control unit comprises means fordetermining that a registration operation for carrying out registrationof a new key has been carried out; and the electronic control unitcarries out the writing of authentication data into the transponder ofthe new key when it determines that the collation result is a match andthat the registration operation has been carried out.
 8. An anti-theftdevice according to claim 5, wherein the electronic control unitcomprises means for, after the writing is carried out, conductingcommunication with the transponder of the new key and checking whetheror not the authentication data has been written into the new keycorrectly, and informing a user registering the new key of the result ofthe check.
 9. An anti-theft device according to claim 5, wherein thetransponders of the registered key and the new key are such that onceauthentication data has been written into the transponder, theauthentication data cannot be read out to the outside from thetransponder.
 10. An anti-theft device according to claim 5, wherein theauthentication data is function data for operating on query data sentfrom the electronic control unit at the time of anti-theftdetermination.
 11. A method for registering a new key in an anti-theftdevice according to claim 5, wherein:the electronic control unitconducts communication with the transponder of the registered keythrough transmission of communication data; and the writing ofauthentication data into the transponder of the new key is done bydisengaging an anti-theft mode when authentication data stored in thetransponder, different from the communication data, is identical toauthentication data stored in the electronic control unit, and isperformed when a new key is subsequently placed in communication withthe electronic control unit.
 12. A method for registering a new key inan anti-theft device according to claim 5, wherein:the electroniccontrol unit conducting communication with the transponder of theregistered key includesthe electronic control unit transmitting querydata to the transponder of the registered key, and preparing responsedata based on authentication data stored in the transponder and thetransmitted query data, and transmitting the prepared response data tothe electronic control unit from the registered key transponder;collating the authentication data in the storing means with theauthentication data in the transponder of the registered key includes,at the electronic control unit, preparing response data based on thequery data and the authentication data stored in the electronic controlunit, and comparing the response data at the electronic control unitwith the response data sent from the transponder; and writing theauthentication data into the transponder of the new key is done when theresponse data at the electronic control unit and the response data sentfrom the transponder are identical.
 13. A method for registering a newkey in an anti-theft device, comprising:preparing a new key having atransponder in which authentication data has not been written;conducting communication between a transponder of a pre-registeredmaster key and an electronic control unit having an anti-theft functionand determining if the communication was conducted correctly; allowingregistration of a new key when determining that the communication wasconducted correctly; and conducting communication between thetransponder of the new key and the electronic control unit and by thiscommunication writing authentication data matching authentication dataof the master key into the transponder of the new key.
 14. A method forregistering a new key in an anti-theft device according to claim 13,wherein communication data sent by the transponder of the master key tothe electronic control unit includes, in addition to the authenticationdata, a key identification code identifying the master key.
 15. A methodfor registering a new key in an anti-theft device according to claim 13,wherein:conducting communication between the transponder of the masterkey and the electronic control unit is done through transmission ofcommunication data; allowing registration of the new key includesdisengaging an anti-theft mode when authentication data stored in thetransponder, different from the communication data, is identical toauthentication data stored in the electronic control unit; and writingauthentication data of the master key into the transponder of the newkey is performed when a new key is subsequently placed in communicationwith the electronic control unit.
 16. A method for registering a new keyin an anti-theft device according to claim 13, wherein:conductingcommunication between the transponder of the master key and theelectronic control unit includestransmitting query data from theelectronic control unit to the transponder of the master key, andpreparing response data based on authentication data stored in thetransponder and the transmitted query data, and transmitting theprepared response data to the electronic control unit from the masterkey transponder; determining if communication was conducted correctlyincludes, at the electronic control unit, preparing response data basedon the query data and the authentication data stored in the electroniccontrol unit, and comparing the response data at the electronic controlunit with the response data sent from the transponder; and writing theauthentication data into the transponder of the new key is done when theresponse data at the electronic control unit and the response data sentfrom the transponder are identical.
 17. A method for registering a newkey in an anti-theft device according to claim 14, wherein a keyidentification code different from the key identification code of themaster key is written into the transponder of the new key in addition tothe authentication data matching the authentication data of the masterkey.
 18. A method for registering a new key in an anti-theft deviceaccording to claim 7, wherein the authentication data and keyidentification codes respectively assigned to a plurality of keys havingthe same authentication data are stored in the electronic control unitand only when recognizing the key identification code of the master keydoes the electronic control unit allow registration of the new key. 19.An electronic control unit for conducting communication with atransponder of an electronic key and controlling the ability of anobject of theft prevention to be operated, the electronic control unitcomprising:storing means for storing authentication data of a properregistered key; determining means for determining by communication withthe electronic key whether or not the electronic key is a registeredkey; permitting means for permitting access to the object of theftprevention when the determining means determines the electronic key tobe a registered key; and mode switching means by which is set a readoutmode enabling the authentication data registered in the storing means tobe sent outside the storing means when the determining means determinesthe electronic key to be a registered key; wherein the authenticationdata is function data for operating on query data sent from theelectronic control unit at the time of anti-theft determination.
 20. Anelectronic control unit according to claim 19, wherein in the readoutmode the authentication data registered in the storing means can be sentto a new key having a transponder in which authentication data has notbeen written.
 21. An electronic control unit according to claim 19,wherein in the readout mode the authentication data registered in thestoring means can be sent to another electronic control unit havingstoring means in which authentication data of a registered key has notbeen written.
 22. An electronic control unit according to claim 19,further comprising:means for determining that a registration operationfor carrying out registration of a new key has been carried out; whereinthe electronic control unit carries out writing of authentication datainto the transponder of the new key when the determining meansdetermines that the electronic key is a registered key and theregistration operation has been carried out.
 23. An electronic controlunit according to claim 19, wherein the authentication data is functiondata for operating on query data sent from the electronic control unitat the time of anti-theft determination.
 24. A electronic control unitfor registering a new key in an anti-theft device according to claim 19,wherein:the determining means is for determining whether the electronickey is a registered key by conducting communication between thetransponder of the registered key and the electronic control unitthrough transmission of communication data; the permitting means is forpermitting access by disengaging an anti-theft mode when authenticationdata stored in the transponder, different from the communication data,is identical to authentication data stored in the electronic controlunit; and further comprising writing means for writing authenticationdata stored in the electronic control unit into the transponder of a newkey when a new key is subsequently placed in communication with theelectronic control unit after the mode switching means sets the readoutmode.
 25. A electronic control unit for registering a new key in ananti-theft device according to claim 19, wherein:the determining meansis for determining whether the electronic key is a registered keybytransmitting query data from the electronic control unit to thetransponder of the electronic key, preparing response data based onauthentication data stored in the transponder and the transmitted querydata, and transmitting the prepared response data to the electroniccontrol unit from the electronic key transponder, and at the electroniccontrol unit, preparing response data based on the query data and theauthentication data stored in the electronic control unit, and comparingthe response data at the electronic control unit with the response datasent from the transponder; and further comprising writing means forwriting the authentication data stored in the electronic control unitinto the transponder of a new key is done when the mode switching meansdetermines that the response data at the electronic control unit and theresponse data sent from the transponder are identical and thus that theelectronic key is a registered key.
 26. An electronic control unitaccording to claim 20, further comprising:means for writing a keyidentification code of the new key into the transponder of the new keyand the storing means; wherein the determining means determines that theelectronic key is a registered key when authentication data and a keyidentification code written in the electronic key match authenticationdata and a key identification code stored in the storing means match.27. An electronic control unit according to claim 20, further comprisingmeans for, after sending the authentication data, conductingcommunication with the transponder of the new key and checking whetheror not the authentication data has been written into the new keycorrectly, and informing a user registering the new key of the result ofthe check.
 28. An electronic control unit according to claim 20, whereinthe transponders of the registered key and the new key are such thatonce authentication data has been written into the transponder, theauthentication data cannot be read out from the transponder.
 29. Ananti-theft device comprising:an electronic control unit having storingmeans for storing authentication data of a pre-registered master key,the electronic control unit being for conducting communication with atransponder of the master key, collating the authentication data storedin the storing means with authentication data written in thetransponder, and determining if the result of the collation is a match,and when the collation result is a match, making starting of an enginepossible; wherein when authentication data is to be written into atransponder of a new key, the electronic control unit conductscommunication with the transponder of the master key and collates theauthentication data stored in the storing means with the authenticationdata written in the transponder of the master key, and when the resultof the collation is a match, allows the writing of authentication datamatching the authentication data of the master key into the transponderof the new key.
 30. An anti-theft device according to claim 29, whereincommunication data sent by the transponder of the master key to theelectronic control unit includes, in addition to the authenticationdata, a key identification code identifying the master key.
 31. A methodfor registering a new key in an anti-theft device according to claim 29,wherein:the electronic control unit conducts communication with thetransponder of the master key through transmission of communicationdata; and the writing of authentication data into the transponder of thenew key is done by disengaging an anti-theft mode when authenticationdata stored in the transponder, different from the communication data,is identical to authentication data stored in the electronic controlunit, and is performed when a new key is subsequently placed incommunication with the electronic control unit.
 32. A method forregistering a new key in an anti-theft device according to claim 29,comprising:the electronic control unit conducting communication with thetransponder of the master key includesthe electronic control unittransmitting query data to the transponder of the master key, andpreparing response data based on authentication data stored in thetransponder and the transmitted query data, and transmitting theprepared response data to the electronic control unit from the masterkey transponder; collating the authentication data in the storing meanswith the authentication data in the transponder of the master keyincludes, at the electronic control unit, preparing response data basedon the query data and the authentication data stored in the electroniccontrol unit, and comparing the response data at the electronic controlunit with the response data sent from the transponder; and writing theauthentication data into the transponder of the new key is done when theresponse data at the electronic control unit and the response data sentfrom the transponder are identical.
 33. An anti-theft device accordingto claim 30, wherein a key identification code, different from the keyidentification code of the master key, is written into the transponderof the new key in addition to the authentication data matching theauthentication data of the master key.
 34. An anti-theft deviceaccording to claim 33, wherein the authentication data and keyidentification codes respectively assigned to a plurality of keys havingthe same authentication data are stored in the electronic control unit,and only when recognizing the key identification code of the master keydoes the electronic control unit allow registration of the new key.